1. Field of the Invention
The invention relates generally to storage systems and more specifically relates to a mounting and enclosure method and apparatus for hot swappable storage devices in a side accessible sled arrangement.
2. Discussion of Related Art
Storage systems, especially larger storage systems, often utilize enclosures that mount in racks/cabinets where each enclosure provides power, cooling, and various other common resources for a plurality of storage devices (e.g., rotating magnetic or optical disk drives as well as solid-state drives). In large storage systems, there may be several such enclosures in a tall rack and potentially several such racks.
In high-reliability storage systems (e.g., RAID storage systems), it is an important aspect that the storage devices may be “hot swapped”—i.e., inserted and removed with power applied. In such systems, a single failed storage device does not result in system failure of the storage system but rather merely degrades performance of the system somewhat until the failed device is replaced with a functioning device and the data of the failed device is rebuilt on the replacement device. The failed device and the replacement device are therefore “hot swapped” such that the storage system continues essentially normal operation while the failure is corrected. To perform hot swaps of storage devices housed within an enclosure, the enclosure may be pulled from the rack (e.g., slid forward on sliding rails) to permit the user to open the enclosure and swap a failed storage device (all performed with power on the enclosure and the storage devices within the enclosure). After hot swapping the failed storage device for a functioning device, the enclosure may be closed and slid back into the rack—again all while the storage devices in the enclosure have power applied and while the storage devices continue operating.
In many large storage systems, rack mounted enclosures can reach significant heights to provide for desired level of storage density in the available floor space. Some enclosures provide for access to all storage devices from the front of the enclosure—the front portion facing an administrative user of the storage system. However, such enclosures provide for very limited storage density in that the only storage devices in the enclosure that are positioned along the front portion of the enclosure are accessible to the administrator for hot swap.
To increase the density of storage in larger storage systems, most present-day enclosures provide access to a larger number of storage devices from the top of the enclosure structure. In such higher density enclosures, an administrative user effectuates a “hot swap” of storage devices by sliding the enclosure out from its rack and accessing the top of the enclosure. To replace a failed storage device (or to perform other administrative services), the enclosure is slid outward from the rack in which it is mounted, a top cover of the enclosure is removed or otherwise opened, and the failed storage device is hot swapped with a replacement device by accessing the open top of the enclosure.
Some racks used to mount enclosure can be quite tall. Accessing the top of an enclosure (i.e., to hot swap a failed storage device) can be, at best, awkward for an administrative user. In some extreme cases, a ladder, stool, or other aid may be required to reach into the enclosure from its opened top side to replace a failed device (or to perform other services). Or, a system designer may require that all high-density storage enclosures be positioned lower in the rack/cabinet to simply avoid such problems for administrative users thus limiting the density of storage that may occupy a given floor space. In addition, when an enclosure mounted near the top of a rack is pulled forward from the rack (extending outward to permit administrator access—with or without a ladder or stool), the rack may become unstable due to the significant weight extending forward from the rack near the top. To reduce this problem, enclosures mounted higher in the rack may be restricted to lower density of storage devices or the rack may be designed with counter-weights or extended feet to support the higher weight mounted near the top.
It is therefore an ongoing challenge to provide high storage density in an enclosure while enabling ease of use for an administrative user to access storage devices within the enclosure (e.g., for hot swap or other administrative functions).